Vernier condenser



March 1943- I DE wm- R. GODDARD 2,313,429

VERNIER CONDENSER Filed lay 25, 1939 I NV EN TOR.

' DE wm' R. GODDARD A TTORN E Y.

Patented Mar. 9, 1943 vnnumn CONDENSER De Witt R11 Goddard, Riverhead, N. Y.,assignor to Radio Corporation America, a corporation of Delaware Application May 25, 1939, Serial No. 275,692

. Claims. (01. via-41.5)

This invention relates to a new and useful ver nier condenser which is particularly adapted for use with a radio receiver. i

An object of this invention is to simplify and improve vemier condensers having a small range of capacity.

Another object of this invention is to provide a small compact vernier condenser unit having two ranges of capacity variation.

In the prior art, whenever it was desirable to cbtain very small ranges of Vernier action on the main tuning condenser ofa receiver, it was customary to use two'vernier condensers, for example, one having a capacity variation range in the order of one percent of the main condenser a'nd the other having a capacity variation range roughly in the order of of one percent of the main tuning condenser. nier condensers naturally add complication to the receiver, increase the cost and frequently require crowding of various component receiver.

parts. The vemier condenser of my invention does away with the necessity of requiring two vernier condensers inthe radio receiver for the reason that the single condenser provides two ranges of capacity variation, the two ranges being obtained by merely moving the position of the condenser operating knob.

This invention will best be understood by referring to the accompanying drawing, in which:

Fig. 1 is an elevation of the condenser looking from the rear; and

Fig. 2 is a longitudinal section of Fig. 1.

Referring now-in detail to the drawing, it will be seen'that the stationary semi-circular condenser plate I is capacitively acted upon by a movable semi-circular condenser plate 2 to obtain the necessary large capacity variations. Stationary plate i is mounted upon an insulating base 3 by means of an angle strip member 4. Movable plate 2 is secured to a metal shaft 5 by means of a collar 6 and a set screw 1. A circular movable plate 8 is likewise secured to shaft 5 by means of collar Q'and set screw i0. An upright or panel It supports a large bushing or shaft bearing (2, which is secured to member II by means of nut IS. The metal shaft 5 on which is secured movable plate 2 and circular plate 8 has two annular grooves or rings machined as indicated at l5 and I6. Shaft bushing I! has an aperture I! in which is located a spherical ballshaped member l8. A spiral spring l9 normally keeps the shaft 5, by means of frictional engagement with ball l8, from moving horizontally through the bushing and yet allows it to Such additional verbe rotated for obtaining the necessary capacity variation. However, a sharp forward pull on knob 20 will move the shaft through bushing l2 until the ball drops into groove l6, thereby locating the condenser shaft and movable plates 2 and 8 in a new position. This new position, which is indicated by dotted lines, provides a much greater clearance or plate spacing between the movable and stationary plates, thereby givinga much smaller range of capacity variation.

This arrangement provides two ranges of capacity for the vernier condenser. However, by

u the addition of the circular plate 8 there is prothat movable plate 8 is so situatedand its spacing and capacitive area proportioned that when shaft 5 is pulled out the condenser knob being set at the mid-scale, its approach to stationary .condenser plate ladds a fixed value of capacity which just compensates for the decrease in capacity due to the increased spacing between the movable condenser plate 2 and the stationary plate I. Due to the fact that plate 8 is circular in shape, it contributes no change in capacity upon the rotation of shaft 5. An advantage of this type of condenser is that it is possible to calibrate or engrave on the dial two separate frequency scales, one applying when groove l5 engages bali iii, the other when groove l6 engages the ball. Then, when the condenser is operated with greater frequency range, 1. e. groove l5 engaging ball l8, one need only to note whether the frequency to which thedial is set is a frequency lying in the range of the other calibration scale, in order to determine whether the particular frequency can be tuned in with the dial in the narrow range position, i. e. groove l6 engaging ball l8.

Although only onemodification of this invention is disclosed, it is distinctly understood that it shoud not be limited in the general scope thereof.

WhatIclaim is:

1. A vemier condenser having two ranges of capacity variation comprising a fixed non-circuand said fixed electrode is the same in both ranges of capacity variation of the condenser in its midposition of rotation, said fixed electrode located intermediate said movable plates to be in capacitive engagement therewith, means to change the capacity range by changing the spaced relationship between said plates and said fixed electrode to give a difi'erent range of capacity.

2. A variable condenser having two ranges oi! capacity variation comprising a semi-circular fixed electrode and a movable semi-circular plate, a circular movable plate, a shaft for rotating said movable plates, said shaft having a pair or annular grooves located thereon, the relative areas of each one or said plates and the distance between said plates and their position with respect to said fixed electrode being so chosen that the total capacity between said plates and said fixed electrode is the same in both ranges or capacity variation of said condenser in its mid-position of rotation, said fixed semi-circular electrode positioned tor capacitive engagement between said movable semi-circular plate and said circular plate, and means adjacent said shaft for engaging said annular grooves whereby said shaft is positioned to change the space relationship between said fixed electrode and both movable plates and thus change the capacity range of the condenser.

3. A variable condenser-having a first and a second capacity range comprising a fixed noncircular electrode, a movable non-circular plate, a shaft for rotating said movable non-circular plate, a pair of annular grooves located on said shaft, a circular plate also located on said shaft, the relative areas 01' each one of said plates and plates and thus change the capacity range 0! the condenser.

4. A variable electric condenser having two alternative ranges or capacitive variation with equal capacity'in each range at a predetermined setting or said variation, said condenser comprising, a non-circular fixed electrode, a rotatable shaft, a circular plate located on said shaft and arranged on one side of said fixed electrode, a non-circular plate located on said shaft and positioned on the other side 01 said fixed electrode, means on said shaft to provide two alternative positions of said plates with respect to said fixed electrode to give a small and large range of capacitive variation, means for axially shitting said shaft between said alternative operative positions as determined by said first mentioned means, the relative areas 0! each one of said plates and the distance between said plates and their position with respect to said fixed electrode being so chosen that the total capacity between said plates and said fixed electrode is the same in both althe distance between said plates and their positernative operative positions when said condenser is set at the predetermined setting of variation.

5. A variable condenser having a first and a second range of capacity variation comprising a fixed non-circular electrode, a movable noncircular plate, a shaft for rotating said movable non-circular plate, a circular plate also located on said shait, said fixed non-circular electrode positioned for capacitive engagement between said non-circular movable plate and said circular plate, the relative areas of each one of said plates and the distance between said plates and their position with respect to said fixed electrode being so chosen that the capacity between said plates and said fixed electrode is the same in both ranges of capacity variation of said condenser in its mid-position of rotation, a bushing surrounding said shaft, a spherical-shaped memher having spring tension means located within said bushing, said shaft having a pair of annular grooves which are located so as to cooperate with said spherical-shaped member to maintain the space relationship between said fixed electrode and movable plates and thus change the capacity range 01 the condenser from one range to another.

DE WI'I'I RUGG GODDARD. 

